1. Field of the Invention
The present invention relates to a control circuit for reducing touch current of a power converter and an operation method thereof, and particularly to a control circuit and an operation method thereof that can reduce touch current generated by quick decrease of a voltage of an input capacitor when a power converter leaves a burst mode.
2. Description of the Prior Art
In the prior art, when a power factor correction (PFC) power converter is in a high output voltage and light load operation, the power converter will enter a burst mode. After the power converter enters the burst mode, a power switch of the power converter can be switched according to a gate control signal corresponding to the burst mode. Meanwhile, because current consumption of the power converter is very small, a voltage of an input capacitor of the power converter will be kept at a voltage when the power switch stops being switched. When the power converter leaves the burst mode, the power switch starts to be switched according to a gate control signal corresponding to a quasi-resonant mode. Meanwhile, if an input voltage is less than the voltage of the input capacitor, diodes within a bridge rectifier of the power converter cannot be conducted, resulting in the input capacitor providing power to an inductor of the power converter. Thus, the voltage of the input capacitor will be decreased. Meanwhile, because the power converter operates in the highest frequency (corresponding to the quasi-resonant mode), the voltage of the input capacitor will be decreased quickly, resulting in a touch current over a standard specified by a safety specification.
In addition, the prior art only adjusts parameters of the power converter to solve a problem of the touch current over the standard, so the prior art only solve the problem of the touch current over the standard partially. Therefore, a designer of the power converter needs to find a new solution to replace with the prior art.